Sydney
17.17 Decrease of inter–region surface water claim on water

Supporting information

The volume recognised in the surface water statements (7,077 ML) recognises the total decrease on the inter–region surface water claim for the Fish River Water Supply Scheme during the 2011–12 year.

Quantification approach

Bureau of Meteorology

Data source

Sydney Catchment Authority; internal databases and New South Wales Office of Water: Fish River Water Supply Scheme Weekly Use Report 2011–12.

Provided by

The Bureau.

Method

Total adjustment and forfeiture on the inter–region claim on surface water is calculated by summing the total carryover and entitlement for the 2011–12 year, and subtracting any diversions made during that year and any carryover into the 2012–13 year.

Each agency has an annual maximum allocation entitlement from the Fish River Water Supply Scheme to supply water to their storages. This entitlement is subject to a number of operating rules and restrictions depending on levels in the supply storages (Oberon Dam and Duckmaloi Weir).

The carryover volume available at the beginning of a year from the Fish River Water Supply Scheme is calculated from entitlement holder's allocation and metered supply volume for the previous two years (carryover volume is a two–year rolling average computed every six months; the carryover volume is capped at 50% of the maximum annual quantity).

Maximum Allocation Entitlement and carryover on the Fish River Water Supply Scheme is shown in the following table.



Maximum allocation limits and carryover on the Fish River Water Supply Scheme during the 2011–12 year

Organisation

Maximum Allocation

Entitlement (ML)

Carryover entitlement
as at 30 June 2011

(ML)

Carryover as at

30 June 2012 (ML)

Sydney Catchment Authority

3,650
119

730

Delta Electricity

8,184

216

1,637

Lithgow City Council1

1,778

36

356

Total

13,612

3712

2,723

1 Lithgow City Council's entitlement includes diversion to storages that are outside the Sydney region boundaries. 

2 Refer to comparative year information below for details on changes to the 2011 volume.


Total forfeiture is calculated as shown in the following table.


Total decrease of claim on inter–region surface water during the 2011–12 year


Volume
(ML)

 

Opening balance 1.5 Inter–region claim on water  (as at 30 June 2011)

371

add

9.15 Increase of inter–region surface water claim on water

13,612

less

9.11 Delivery of water under inter–region agreement to surface water

4,183
less
Closing balance 1.5 Inter–region claim on water (as at 30 June 2012) 2,723


Total decrease on claim (as at 30 June 2012)

7,077

Assumptions, limitations, caveats and approximations

It is assumed that the maximum allocation entitlement held by each organisation for the Fish River Water Supply Scheme represents the total allocation for the region.

Uncertainty information

Carryover volume is based on measured data. Estimated uncertainty based on meter accuracy is +/– 2%.

Comparative year

This line item corresponds to line item 17.17 Decrease of inter–region claim on water reported in the 2011 Account.

In the 2010–11 year, this line item only included the Sydney Catchment Authority's decrease of inter–region claim on the Fish River Water Supply Scheme. In the 2011–12 year, this line item now also recognises Delta Electricity and Lithgow City Council decrease on claim from the Fish River Water Supply Scheme which was previously reported in 19.14 Decrease of urban inter–region claim on water (45 ML). As the inter–region claim is now recognised as the total Maximum Annual Allocation Entitlement on the Fish River Water Supply Scheme the volume has been restated from 3,201 ML to 4,510 ML.